title: Identification and quantitation of all-trans- and 13-cis-retinoic acid and 13-cis-4-oxoretinoic acid in human plasma.
abstract: Human plasma was analyzed by high performance liquid chromatography for the presence of retinoic acid and 4-oxoretinoic acid isomers. Peaks that coeluted with the reference compounds all-trans-retinoic acid, 13-cis-retinoic acid, and 13-cis-4-oxoretinoic acid were routinely observed in human plasma. These retinoids were unequivocally identified by the following methods: comigration with reference compounds under several high performance liquid chromatographic conditions; comparison of ultraviolet spectra with those of reference compounds; derivatization with diazomethane and coelution of the methyl esters with reference compounds in a high performance liquid chromatographic system as well as in a gas chromatography system with a mass selective detector. In vitro formation of 13-cis-retinoic acid and 13-cis-4-oxoretinoic acid as artifacts during the analytical procedure was excluded by control experiments. The mean plasma concentrations of the vitamin A metabolites in ten male volunteers were: all-trans-retinoic acid: 1.32 +/- 0.46 ng/ml; 13-cis-retinoic acid: 1.63 +/- 0.85 ng/ml; and 13-cis-4-oxoretinoic acid: 3.68 +/- 0.99 ng/ml. After oral dosing with vitamin A (833 IU/kg body weight) in five male volunteers, mean plasma all-trans-retinoic acid increased to 3.92 +/- 1.40 ng/ml and 13-cis-retinoic acid increased to 9.75 +/- 2.18 ng/ml. Maximal plasma 13-cis-4-oxoretinoic acid concentrations (average 7.60 +/- 1.45 ng/ml) were observed 6 h after dosing which was the last time point in this study. Concentrations of all-trans-4-oxoretinoic acid were low or not detectable. Our findings suggest that, in addition to all-trans-retinoic acid, 13-cis-retinoic acid and 13-cis-4-oxoretinoic acid are present in normal human plasma as metabolites of vitamin A.
authors.affiliation: Institut für Toxikologie und Embryonalpharmakologie, Freie Universität Berlin, West Germany.
authors.forename: C
authors.initials: C
authors.lastname: Eckhoff
authors.forename: H
authors.initials: H
authors.lastname: Nau
mesh_terms: D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D003978:Diazomethane; D006801:Humans; D015474:Isotretinoin / Q000097:blood*; D008297:Male; D013056:Spectrophotometry, Ultraviolet; D014212:Tretinoin / Q000031:analogs & derivatives* / Q000097:blood*; D014801:Vitamin A / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D014801:Vitamin A; C002202:4-oxoretinoic acid; D014212:Tretinoin; D003978:Diazomethane; D015474:Isotretinoin